Various exhaust after-treatment devices have been developed to effectively limit exhaust emissions from internal combustion engines. An after-treatment system for a modern diesel engine exhaust typically incorporates a diesel oxidation catalyst (DOC), a selective catalytic reduction (SCR) catalyst, and a diesel particulate filter (DPF).
The DOC is primary responsible for reduction of carbon monoxides (CO) and non-methane hydrocarbons (NMHC), and can also be employed to generate nitrogen dioxide (NO2), which is required by the SCR that is arranged downstream of the DOC. The SCR is configured to convert NOx into diatomic nitrogen (N2) and water (H2O) with the aid of the NO2 generated by the DOC. The DPF primarily takes care of collecting and disposing sooty particulate matter (PM) emitted by the diesel engine prior to the exhaust gas being discharged to the atmosphere.
A typical after-treatment system also includes a number of sub-systems designed to enhance operation of the after-treatment devices, along with multiple temperature probes for sensing exhaust gas temperature at various locations within the subject system. Accurate assessment of exhaust gas temperature data is essential for precise control of the engine in general, and the AT system in particular.